Pd and Pd,In nanoparticles supported on polymer fibres as catalysts for the nitrate and nitrite reduction in aqueous media

Abstract

The presence of high concentrations of nitrate and nitrite ions in water sources is an actual environmental problem. Nowadays, there are several technologies for nitrate and nitrite treatment, but most of them involve the concentration of the ions which are later necessary to be decomposed in a second step. The catalytic elimination of nitrates and nitrites from water is a very promising method because the ions are transformed into the harmless N2(g). Two types of synthetic polymeric fibers were proposed as supports of palladium and indium catalytic species with low metallic loading (Pd:In = 1:0.25 wt.%). They were synthesized by electrospinning method with a Pd/In weight ratio 1:0.25. PdInDA catalyst was prepared by dissolving poly (methyl methacrylate) (PMMA) with a mixture of acetone/dimethylformamide, whereas the polymer (PMMA) was dissolved in pure dimethylformamide for the synthesis of PdD and PdInD catalysts. Both bimetallic solids gave rise to good selectivity to N2(g). However, the PdInDA reached middle nitrate conversions (around 50 %) with low ammonia production (under 0.1Nppm). The characterization results suggested that the active sites remained unchanged after the reaction. This proposal involves a green chemical method with low consumption of reactants and producing a small quantity of waste.